A transmission of a vehicle, which has a traveling transmission path for transmitting power from a driving power source to a pair of left and right main driving wheels and a PTO transmission path for transmitting power from the driving power source to a PTO shaft, has been conventionally known.
For example, a prior document 1 mentioned below discloses a transmission in which the traveling transmission path is formed by an HST operatively connected to the driving power source, a planetary gear mechanism respectively receiving constant-speed rotational power and variable-speed rotational power from a pump shaft and a motor shaft of the HST, a traveling gear speed change mechanism receiving a rotational power output from the planetary gear mechanism and a differential gear mechanism disposed on a downstream side of the traveling gear speed change mechanism in a power-power-transmitting direction.
The transmission is effective in terms of transmission efficiency because a part of the power transmitted through the traveling transmission path is not converted to hydraulic pressure.
However, the transmission leaves a room for improvement with respect to compact arrangement of the traveling transmission mechanism and the PTO transmission mechanism.
A prior document 2 discloses a transmission including a transmission case, an HST connected to a front surface of the transmission case, and a traveling gear speed change mechanism, a differential gear mechanism, a PTO clutch mechanism and a PTO gear speed change mechanism that are disposed in the transmission case, the transmission having a traveling transmission path for transmitting power from an output shaft of the HST to a pair of main driving wheels via the traveling gear speed change mechanism and the differential gear mechanism, and a PTO transmission path for transmitting power from an input shaft of the HST to a PTO shaft via the PTO clutch mechanism and the PTO gear speed change mechanism.
The conventional transmission is configured to respectively arrange the traveling transmission path and the PTO transmission path on left and right sides in a front view in order to prevent the transmission paths from being interfered with each other. However, the transmission leaves a room for improvement with respect to downsizing of the transmission as a whole.
In other words, in the above conventional transmission, the PTO transmission path is formed by the HST input shaft disposed vertically above the HST output shaft, a PTO speed change shaft disposed on a lower and a right side of the HST input shaft in a front view, an interlocking shaft and a mid PTO shaft disposed in order below the PTO speed change shaft, and a rear PTO shaft disposed above the PTO speed change shaft. This arrangement causes a problem that the overall transmission becomes large, especially in a vertical direction.
Further, the traveling transmission path in the above conventional transmission includes the HST output shaft disposed vertically below the HST input shaft, a traveling speed change shaft disposed on a upper side and a left side of the HST output shaft in a front view, a reduction gear for reducing speed of rotational power of the traveling speed change shaft and transmitting it to the differential gear mechanism, a traveling transmission shaft disposed below the traveling speed change shaft, and a front-wheel driving shaft disposed on a left side of the traveling speed change shaft in a front view. However, the arrangement causes a dead space on an upper side of the traveling speed change shaft and on a left side of the HST input shaft in a front view. As a result, the transmission is not enough in terms of downsizing.
In consideration of the conventional arts, it is an object of a first aspect of the present invention to provide a transmission of a vehicle, which includes a traveling transmission path for transmitting power from a driving power source to a pair of left and right main driving wheels via an HST, a traveling gear speed change mechanism and a differential gear mechanism, and a PTO transmission path for outputting power from the driving power source outside via a PTO clutch mechanism, the transmission being capable of accommodating transmission mechanisms forming the traveling transmission path and the PTO transmission path in a compact manner.
Moreover, the prior document 2 proposes a transmission including the transmission case, the HST connected to one end surface of the transmission case, and the traveling transmission mechanism and the PTO transmission mechanism positioned on a downstream side of the HST and accommodated in the transmission case, the transmission being capable of drawing oil stored in the transmission case through a suction filter provided at the one end surface of the transmission case.
The oil stored in the transmission case can be utilized as an oil source of charge oil for the HST forming a part of the traveling transmission mechanism, for example. Therefore, a separate oil tank can be eliminated or reduced in size.
Incidentally, the transmission including the traveling transmission mechanism and the PTO transmission mechanism as described above may be provided with a sub-traveling output shaft and a sub-PTO shaft in addition to a main traveling output shaft and a main PTO shaft according to its specification.
With regard to this point, the prior document 2 discloses a configuration in which a front-wheel power takeoff shaft functioning as the-sub traveling output shaft and a mid PTO shaft functioning as the sub-PTO shaft are provided at the one end surface of the transmission case to which the HST is connected.
As described above, although there is proposed the configuration that the HST, the sub-starveling output shaft, the sub-PTO shaft and the suction filter are provided at the same wall surface of the transmission case, no consideration is given to efficient arrangement of them.
Specifically, if the HST, the sub-traveling output shaft, the sub-PTO shaft and the suction filter are provided at the same wall surface of the transmission case, it is needed to take into consideration interference between transmission shafts and a conduit that are connected thereto. However, this viewpoint is not sufficiently taken into consideration in the prior art.
In consideration of the conventional part, it is an object of a second aspect of the present invention to provide a transmission of a vehicle, which includes a traveling transmission mechanism having an HST, a PTO transmission mechanism having a PTO clutch mechanism, and a transmission case that is capable of storing oil therein and that has one end wall to which the HST, a sub-traveling output shaft, a sub-PTO shaft and a suction filter are provided, the transmission allowing transmission shafts connected to the HST, the sub-traveling output shaft and the sub-PTO shaft and a conduit connected to the suction filter to be arranged without difficulty while preventing the transmission case from being enlarged.
Furthermore, the transmission described in the prior document 1 includes, in addition to the traveling transmission mechanism and the PTO transmission mechanism, an auxiliary pump transmission mechanism for transmitting the power from the driving power source to an auxiliary pump main body.
To put it more specifically, he conventional transmission is configured so that the HST is connected to a front wall of the transmission case and power transmission to the auxiliary pump main body supported at a rear wall of the transmission case is performed through an auxiliary pump transmission shaft disposed coaxially with a pump shaft of the HST.
In the conventional transmission, the auxiliary pump transmission shaft and various PTO rotational shafts forming the PTO transmission mechanism extend above a pair of differential output shafts in the differential gear mechanism and in a longitudinal direction of the vehicle.
Therefore, in order to avoid interference between the auxiliary pump transmission shaft and the PTO rotational shafts with the differential gear mechanism, it is needed that the HST and the differential gear mechanism are displaced in a width direction of the vehicle, resulting in enlargement of the transmission case in the width direction of the vehicle.
In consideration of the above conventional art, it is an object of a third aspect of the present invention to provide a transmission of a vehicle, which includes an HST, a traveling gear speed change mechanism, a differential gear mechanism, a PTO clutch mechanism, an auxiliary pump unit, and a transmission case which accommodates the traveling gear speed change mechanism, a differential gear mechanism and a PTO clutch mechanism, the transmission case including a first end wall which is positioned on one side in a longitudinal direction of the vehicle and to which the HST is connected and a second end which is positioned on the other side in the longitudinal direction of the vehicle, to which the auxiliary pump unit is connected and from which a main PTO shaft is extended outward, the transmission being capable of effectively arranging a transmission shaft along the vehicle longitudinal direction so as to be astride the differential gear mechanism to thereby downsize the transmission case as much as possible.
The transmission described in the prior document 1 also leaves a room for improvement with respect to compact arrangement of the traveling transmission mechanism and the PTO transmission mechanism.
Specifically, in the conventional transmission, the HST is disposed on one side of the differential gear mechanism in the longitudinal direction of the vehicle and power transmission to the differential gear mechanism is performed from the other side in the longitudinal direction of the vehicle.
The arrangement causes a plurality of traveling rotational shafts and PTO rotational shafts to extend in the longitudinal direction of the vehicle above the differential gear mechanism. As a result, it becomes difficult to install a brake operating shaft and a differential lock operating shaft, which are disposed to be along the width direction of the vehicle.
In consideration of the conventional art, it is an object of a fourth aspect of the present invention to provide a transmission that includes a traveling transmission mechanism having an HST, a planetary gear mechanism, a traveling gear speed change mechanism and a differential gear mechanism, and a PTO transmission mechanism having a PTO clutch mechanism, the transmission being capable of securing a free space as large as possible above the differential gear mechanism without enlarging a transmission case.
It is desired that the transmission having the traveling transmission mechanism and the PTO transmission mechanism as described in the prior document 1 is adaptable to various specifications according to the type of usage.
Specifically, it is desired that the transmission is adaptable to, for example, one specification having the sub-PTO shaft in addition to the main PTO shaft and another a specification in which a rotational direction of the main PTO shaft can be changed while using common components as much as possible.
However, there is no transmission made in consideration of such viewpoints.
In consideration of the above conventional art, it is an object of a fifth aspect of the present invention to provide a transmission of a vehicle, which includes a traveling transmission path for transmitting power from a driving power source to a pair of left and right main driving wheels via an HST, a traveling gear speed change mechanism and a differential gear mechanism, and a PTO transmission path for outputting power from the driving power source outside from a main PTO shaft via a PTO clutch mechanism, the transmission being capable of easily changing one specification in which power output to the outsides could be performed a sub-PTO shaft in addition to the main PTO shaft to/from another specification in which a rotational direction of the main PTO shaft could be changed.    Prior document 1: Japanese Patent Application Laid-open No. 2003-207021    Prior document 2: Japanese Patent No. 3636594